I'd like to announce the release of sysdrawing-coregraphics with support for Unified.
sysdrawing-coregraphics is an implementation of much of the System.Drawing API using CoreGraphics for the implementation. This means it has support for both Xamarin.Mac and Xamarin.iOS.
This project has been around for awhile with Classic support, but now has been updated to work with Unified Xamarin.Mac/Xamarin.iOS.
Download the build here: http://download.xamarin.com/system-drawing/sysdrawing-coregraphics-Cycle6.zip
View the project here: https://github.com/mono/sysdrawing-coregraphics
Samples are here: https://github.com/mono/sysdrawing-coregraphics/tree/master/Samples
Please note, this is a community project, and not an officially supported part of the Xamarin platform.